Method isetitem

pandas/core/frame.py:4503–4557

Set the given value in the column with position `loc`. This is a positional analogue to ``__setitem__``. Parameters ---------- loc : int or sequence of ints Index position for the column. value : scalar or arraylike Value(s)

(self, loc, value)

        return series._values[loc]

    def isetitem(self, loc, value) -> None:
        """
        Set the given value in the column with position `loc`.

        This is a positional analogue to ``__setitem__``.

        Parameters
        ----------
        loc : int or sequence of ints
            Index position for the column.
        value : scalar or arraylike
            Value(s) for the column.

        See Also
        --------
        DataFrame.iloc : Purely integer-location based indexing for selection by
            position.

        Notes
        -----
        ``frame.isetitem(loc, value)`` is an in-place method as it will
        modify the DataFrame in place (not returning a new object). In contrast to
        ``frame.iloc[:, i] = value`` which will try to update the existing values in
        place, ``frame.isetitem(loc, value)`` will not update the values of the column
        itself in place, it will instead insert a new array.

        In cases where ``frame.columns`` is unique, this is equivalent to
        ``frame[frame.columns[i]] = value``.

        Examples
        --------
        >>> df = pd.DataFrame({"A": [1, 2], "B": [3, 4]})
        >>> df.isetitem(1, [5, 6])
        >>> df
              A  B
        0     1  5
        1     2  6
        """
        if isinstance(value, DataFrame):
            if is_integer(loc):
                loc = [loc]

            if len(loc) != len(value.columns):
                raise ValueError(
                    f"Got {len(loc)} positions but value has {len(value.columns)} "
                    f"columns."
                )

            for i, idx in enumerate(loc):
                arraylike, refs = self._sanitize_column(value.iloc[:, i])
                self._iset_item_mgr(idx, arraylike, inplace=False, refs=refs)
            return

        arraylike, refs = self._sanitize_column(value)
        self._iset_item_mgr(loc, arraylike, inplace=False, refs=refs)

    def __setitem__(self, key, value) -> None:
        """